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In this work, lignocellulosic biomass, namely, Opuntia ficus indica cords (OFIC), was selected as a renewable resource for the production of activated carbon. The preparation conditions of chemically activated carbon (AC) samples were the following: activation temperature -- 600 °C, heating rate -- 10 °C min-1, activation time -- 60 min, and OFIC/H3PO4 impregnation ratio -- 1/2. The properties of OFIC and activated carbon were determined by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), Boehm's method, and pHzpc. AC showed heterogeneous surface and acidic characteristics with a pHZPC of 2.61. OFIC and AC were used as adsorbents to remove the anionic dye Red Bemacid (RB) from aqueous solutions. OFIC was used as a reference for comparison with the prepared AC. The results showed that the experimental data fitted very well with the pseudo-second-order nonlinear model of both adsorbents, with 120 min as equilibrium time and the nonlinear isotherm models of three parameters (Sips and Redlich-Peterson isotherms) were selected as the best fitting ones. The thermodynamic parameters indicated that the adsorption process was spontaneous and endothermic for the AC/RB dye system [ABSTRACT FROM AUTHOR]

Heavy metal contamination is a major concern, and the adsorption process is regarded as one of the most efficient water remediation processes to deal with it. Herein, we modified fly ash by a microwave-assisted hydrothermal process to enhance its adsorption capacity and tested the material toward Cd(II) and Cu(II). Characterization of the adsorbents was performed by several techniques in detail to elucidate considerable structural changes such as cracking of spherical morphology, increase in surface area and changing of the chemical composition. Then batch adsorption was performed under different conditions to investigate the equilibrium, kinetics, and thermodynamics of the process. NaOH-modified fly ash considerably has a higher adsorption performance than that of the as-received sample for both ions. The highest adsorption capacity of modified fly ash was achieved as 133.8 and 95.7 mg/g for Cd(II) and Cu(II), respectively. The kinetics and isotherms could be perfectly reflected by a pseudo-second-order rate equation and the Freundlich model, while thermodynamics confirmed the endothermicity of the process. [ABSTRACT FROM AUTHOR]

Cost-effective activated carbons for CO2 adsorption were developed from molasses using H2SO4, H3PO4, HCl, NaOH, and KOH as activating agents. At the temperature of 0 °C and a pressure of 1 bar, CO2 adsorption equal to 5.18 mmol/g was achieved over activated carbon obtained by KOH activation. The excellent CO2 adsorption of M-KOH can be attributed to its high microporosity. However, activated carbon prepared using HCl showed quite high CO2 adsorption while having very low microporosity. The absence of acid species on the surface promotes CO2 adsorption over M-HCl. The pore size ranges that are important for CO2 adsorption at different temperatures were estimated. The higher the adsorption temperature, the more crucial smaller pores were. For 1 bar pressure and temperatures of 0, 10, 20, and 30 °C, the most important were pores equal and below: 0.733, 0.733, 0.679, and 0.536 nm, respectively. [ABSTRACT FROM AUTHOR]